1. Field of the Invention
The present invention relates to a syringe, and more particularly to a syringe with a snapping device for backward pulling the needle into the syringe after syringing.
2. Description of Related Art
A conventional syringe in accordance with the prior art shown in FIGS. 19 and 20 comprises a hollow barrel (81), a snapping device (82) secured in a first end of the hollow barrel (81), a needle hub (83) securely connected to the snapping device (82) and extending through the hollow barrel (81) and the plunger (84) movably received in the hollow barrel (81).
The hollow barrel (81) includes an annular protrusion (811) extending from the inner periphery of the hollow barrel (81). The snapping device (82) includes a body (not numbered) having a through hole (not numbered) centrically defined in the body. A concave (821) is defined in the outer periphery of the body to partially receive the protrusion (811) of the hollow barrel (81). A hollow stub (822) centrically extends from the body toward the first end of the hollow barrel (81). The needle hub (83) is securely connected to the hollow stub (822). The snapping device (82) includes an annular hook (823) from on an inner periphery of the through hole in the body of the snapping device opposite to the needle hub (83).
The plunger (84) includes a first end movably received in the hollow barrel (81) and a bulb (841) attached to the first end of the plunger (84). The bulb (841) abuts the inner periphery of the hollow barrel (81). An arrow (842) centrically extends from the bulb (841) toward the snapping device (82).
When finishing syringing, the arrow (842) is inserted into the through hole in the body of the snapping device (82) and engaged to the hook (823) to form a connection stronger than that between the annular protrusion (811) and the concave (821). Consequently, the snapping device (82) and the needle hub with the needle are pulled into the hollow barrel (81) to prevent the medical workers from being pricked and accidentally infected by the used needle when the plunger (84) is backward pulled after syringing.
However, the snapping device (82) is connected to the hollow barrel (81) only by the protrusion (811) being received in the concave (821) in the snapping device (82). Consequently, the snapping device (82) is securely connected to the hollow barrel (81) when the protrusion (811) has a height greater than a depth of the concave (821) to prevent the snapping device (82) from falling into the hollow barrel (81) when mounting the needle hub (83) onto the hollow stub (822) of the snapping device (82). However, the plunger (84) cannot backward pull the snapping device (82) and the needle hub (83) into the hollow barrel (81) after syringing when the connection between the snapping device (82) and the hollow barrel (81) is greater than that between the snapping device (82) and the arrow (842) of the plunger (84) such that the needle will expose out of the hollow barrel (81) and hurt the medical workers. On the contrary, the connector will fall into the hollow barrel (81) when attaching the needle (83) to the snapping device (82).
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional syringe with a snapping device.